"There are not a lot of crabs. You've got a few guys crabbing," said Merlin Schaefer with Bucktown's Schaefer and Rusich Seafood.

Lake Pontchartrain is about to become a whole lot fresher, and saltwater species like crabs, shrimp and specks will likely move further east after the spillway is opened.

"Whatever out there is going to push it, since not being used to that water, it will push crabs and shrimp," Schaefer said.

And when the shrimp go, so will the specks.

"That will push some fish like trout to stay in salty water," said John Lopez with the Lake Pontchartrain Basin Foundation.

Within two weeks, will replace, all of one of the country's largest lakes with river water, and while some believe the earlier, colder weather should help the lake bounce back, there are no guarantees.

"There are a lot of variables. If we have an early warming in the spring, we could see blooms," said Lopez.

The spillway opening is just the latest setback for Lake Pontchartrain crabbers who have dealt with a lot of setbacks in recent years.

"They've been down in the lake, but crabs are good in St Bernard and Plaquemines," said Lopez.

First Hurricane Katrina, then the BP spill, then Isaac made Pontchartrain crab and shrimp production a shadow of what it once was. But things had been improving. Shrimp came back last summer, and so did crabs.

"Flexibility is the whole thing. That's it. I learned that in the last twelve years," Schaefer said.

While the river water pushes some out, new species, like carp, will come in.

"The Corps will also be monitoring sturgeon. The Corps would like to put them back into the river," Lopez said.

It's a constant ebb and flow, this year driven by winter rainstorms in the Midwest, which produced a side benefit.

"Crawfish are good this year. That's one thing about the river being a little high," said Schaefer.

Impacts on the lake could be felt until late summer.

"Normally the system is rebounding by the following fall," Lopez said.

But veteran fishermen and biologists are confident the lake will fully bounce back

If all goes according to plan, the Corps expects to keep the spillway open for several weeks. They say they have a detailed environmental monitoring plan in place, designed to check everything from water quality to impacts on fish.